Data Science Lab Conducted Tests on Users With Little Oversight

Thousands of Facebook Inc. users received an unsettling message two years ago: They were being locked out of the social network because Facebook believed they were robots or using fake names. To get back in, the users had to prove they were real.

In fact, Facebook knew most of the users were legitimate. The message was a test designed to help improve Facebook's antifraud measures. In the end, no users lost access permanently.